The present invention generally relates to micro-electro-mechanical system (MEMS) and their fabrication. More particularly, this invention relates to a MEMS module capable of storing energy over an extended period of time by preventing charge leakage while allowing controlled charge transfers to and from an integrated energy storage device through the use of integrated MEMS switches. The MEMS switches can be adapted to be responsive to one or more external inputs, such as an environmental, chemical, or biological parameter, and the charge transfer through the switches can be utilized to power electronic circuits or store data in non-volatile digital memory, for example, to provide an output that correlates the charge transfer to an external input to which the switches are responsive.
Wireless sensor systems enable ambient intelligence, total visibility, and smart adaptive systems while having the capability of high reliability, efficiency, and performance. Such systems impact a wide range of applications including supply-chain and logistics, industrial and structural monitoring, healthcare, homeland security, and defense. Generally, it is desired to minimize the power dissipation, size, and cost of these systems by making them low-power and/or operate without a battery. Furthermore, in many applications a batteryless operation is needed due to lack of battery replacement feasibility, or to meet stringent cost, form factor, and lifetime requirements. One approach to address this need is scavenging energy from environmental sources such as ambient heat, radio and magnetic waves, vibrations, and light. However, in many situations, these environmental energy sources are not adequately available to power a sensor. Another approach is to remotely power a wireless sensor systems by inductive or electromagnetic coupling, storing energy on a suitable energy storage device, such as one or more integrated capacitors or miniature batteries, and performing sensor operations over short periods of time prior to minimize that discharge rate of the energy storage device.
A common drawback to the above sensor systems is the tendency for energy storage devices to discharge over extended periods of time, often as a result of charge leakage through the connected circuitry. This operational issue can be addressed with the use of sensors that do not require an external energy source for sensing, as their operations are based on chemical reactions or mechanical events that produce a color or other property change that can be detected by visual inspection or through the use of an electronic detection system. However, such sensors are generally limited to sensor labels and do not easily lend themselves to automation.
In view of the above, it would be desirable if devices requiring an energy storage capability were able to be powered over extended periods, yet provide a desirable level of functionality as compared to devices that do not have or require an energy storage capability.